<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
      box-sizing: border-box;
    }
    .thumb-responsive {
      display: flex;
      flex-wrap: wrap;
    }
    .thumb-responsive a {
      width: calc(100% / 3);
      padding: 0 10px;
      margin-bottom: 20px;
    }
    .thumb-responsive a img {
      display: block;
      max-width: 100%;
      height: auto;
    }
  </style>
</head>
<body>
  <div style="max-width: 350px; margin: 0 auto;">
    <div class="thumb-responsive">
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
      <a><img src="./images/thumb.png" alt=""></a>
    </div>
  </div>

</body>
</html>